1980s: made a lot of questionable
inventions, such as
"Scherflieg" (scissors-fly, failed patent EZK/D 567.884.030).
Scherflieg's drawback: it requires a significant physical effort,
and the user soon starts to spin in the direction
opposite to the rotor's. Most people who tried Scherflieg were not able
to stay airborne for more than 30 seconds, or to reach altitudes
above 10 meters. Future models will have a second rotor with opposite spin.